Nature 2017 February

Concluding with some weasel words

Each year on the last weekend of January along with, according to the RSPB, over 519,000 others I take part in their Big Garden Birdwatch. It has the advantage of being straightforward to participate, only takes an hour and does not even require one to sit out in the inclement weather.

It is staged at this time of the year for several reasons: it is easier to see the birds when there are no leaves on the trees; the winter cull of weaker birds has already occurred so year-on-year populations are more comparable and regular winter visitors will have already arrived. The highlight of my tick list last time was the arrival on cue of two of our regular red kites and also a gaggle of nine long-tailed tits. Meanwhile, having seen a long-standing resident crew of magpies increase in numbers, they have thankfully largely disappeared, which is good news for nesting birds.

At the time of writing there are visiting flocks of redwings competing with thrushes, blackbirds and the odd fieldfare, another seasonal arrival. Not only are birds easier to spot in the winter they can, under the right conditions, be easier to identify by their signature tunes. This is because several garden bird species at this time of the year use song to make claims on or reinforce their territories. In a few cases both the males and females ‘hold’ their own territories in winter and so both sing to make their presence heard by potential rivals.

For example, it’s likely the first tune you hear will be that of a robin which is very strident at this time of year. The songs of wrens are characterised by powerful outbursts way out of proportion to their size. Other garden birds make their mark or get themselves noticed by being distinctly untuneful: for example, the  nuthatch or starling. As dust settles an adolescent tawny owl might make an occasional outburst. If you hear the melodious tune of a song thrush it will be a male, as female song thrushes do not sing. Meanwhile their relative, the blackbird, remains silent.

There are a few open fields round here where you might come across brown hares. Hares arrived in Britain probably around the time of the Roman Conquest and their spread in lowland Britain may have coincided with the progressive clearance and intensification of farming under the auspices of the invading army. Today, hares are most abundant where a patchwork of crops and pastures provides a good year-round supply of food: what traditionally would be called “old-fashioned mixed farmland.”

It is more than a country tale that March is the start of a time of the year when hares display eccentric behaviour – proverbially they are said to go mad. More descriptively, a small group of hares might suddenly break off from quietly grazing and, without apparent reason, start to ‘lollop’, or chase one another in twos, threes or fours around a field in a circle. Periodically two hares might display by rearing up on hind legs and chaotic flailing of forepaws follows. The madness of the March Hare! Early theories of animal behaviourists wrongly described this to be bouts between two males, fighting over a female (or doe) but it is now known that the aggressor might be a female rebuffing over-eager males.

Unlike Rabbits, which raise their young underground, young hares (leverets) reside in shallow depressions called forms. They are born fully furred, eyes open and are almost immediately capable of running; though rely on absolute stillness for safety. The leverets come together briefly after dusk for their mother to suckle them before returning to the safety of their individual forms. They will be weaned in only three weeks though they start to leave the forms and graze after a fortnight. Adults are typically solitary but may sometimes feed in loose gatherings with one or more lookouts – much like meerkats.

The larger meat-eating mammals, such as foxes and badgers are underground much of the time in late winter and if out and about are keeping a lower than otherwise profile. Weasels on the other hand need to continually stock up on high-energy food. Their traditional hunting ground is woodland, where open country is criss-crossed with hedgerows, or otherwise anywhere that can provide cover across open ground. The most likely time to spy a weasel is when it bounds across a road. There is hardly any time to distinguish its features.

Gilbert White, the eighteenth-century naturalist and curate of Selborne, described the Weasel as “not much bigger than a field-mouse… it has a very long slender reddish body, white-breasted and with sooty-coloured pointy ears.” Their reputation as ferocious killers belies the fact that weasels are specialist hunters favouring above all rabbits, rats, voles and mice. As populations of these fluctuate over the year, weasels’ ferocious reputation comes from their habit of “surplus killing”, that is, killing more prey than is immediately required. The surplus is secreted away for later consumption.

Robert Burton, the naturalist who used to write nature notes for the Daily Telegraph, talks of finding a cache of twenty or more dead voles and the importance of surplus killing for females when nursing a family and so unable to hunt. Weasels are not averse to killing birds or taking eggs and chicks of ground-nesting game birds. Even tree-dwelling birds are vulnerable as weasels have the ability to raid hole-nesting birds such as great tits. The long, slender body of weasels also allows them to chase rodents down burrows.

With all hunters, from the cheetah downwards, strenuous effort causes excess body heat and drains away muscle rapidly. To counter this, the daily food requirement of a weasel is about one third of its body weight. Weasels will starve if they go hungry for much longer than a day. In fact, the majority of weasels die within their first year. In good years, on the other hand, when food is plentiful females produce two litters.